Lobe switching antenna



y 20, 1954 J. E. EATON LOBE SWITCHING ANTENNA Filed March 29, 1946 INVENTOR JAMES E. EATON ATTORNEY Patented July 20, 1954 LOBE SWITCHINGANTENNA James E. Eaton, Cambridge, Mass, assignor, by mesne assignments,to the United States of America as represented by the Secretary of theNavy Application March 29, 1946, Serial No. 657,993

12 Claims. 1

This invention relates to an antenna, and more particularly to amultiple dielectric rod, lobeswitching antenna.

A lobe-switching antenna is sometimes used as the means for securingaccurate angular data for radar systems. One conventional type oflobeswitching antenna comprises an array divided into several sectionsof radiators, each section being alternately excited by the transmitteroutput current. The separate sections are usually provided withdifferent electrical or physical characteristics, in the well knownmanner, to produce a displacement of the radiation pattern off the axisof the array. Although satisfactory for some applications, such anarrangement is usually quite bulkly physically and is mechanicallyrelatively complex. For some applications, such as airborneinstallations, an antenna which combines lobe-switching functions withdesirable aerodynamic features is necessary.

It is, therefore, an object of this invention to provide alobe-switching antenna.

It is another object of this invention to provide a lobe-switchingantenna having desirable aerodynamic features such that its physicalconfiguration can be designed to conform approximately to a planeairfoil.

These and other objects will be more apparent upon consideration of thefollowing description, together with the accompanying drawings, inwhich:

Fig. 1 is a perspective View of an embodiment of the invention; and

Fig. 2 is a view of a desirable type of excitation probe which can beused to excite the antenna shown in Fig. 1.

Referring to Fig. 1, a first dielectric rod radiator it comprising aslab of dielectric material, such as polystyrene, and having arectangular cross section, is disposed Within the upper channel (asviewed in Fig. 1) of a metallic structure it having an H-shaped crosssection formed by a central reflecting web 9 and integral supportingside pieces 7 and s. A second dielectric rod radiator i2 is disposedwithin the lower open channel of structure I l, opposite radiator H).

A rectangular metal box 13 having one side open is fastened over one endof the above described assembly, with the central web 9 and thedielectric material of radiators l0 and I2 extending within box 13through its open side. The inner conductor of a coaxial line It isextended a predetermined distance within box 53, midway between the sidewalls of rod radiator Ill and at a predetermined distance from theenclosed side of box l3 opposite the open side, to form an excitingprobe 5. The vector direction of the electric component of theelectromagnetic field produced within box 13 and radiator it} is thusperpendicular to the central web ii of the H-shaped structure I I whenprobe 55 is energized by an external source of electromagnetic energy(not shown) coupled to coaxial line id.

A second coaxial line it and probe ll, similar to line It and probe it,provide means for excit ing the second dielectric radiator i 2.

Dielectric radiators l6 and i2 and metal web 9 re tapered longitudinallyby a reduction in the wide dimension of the cross section to provide asatisfactory radiation pattern, a well-known technique in the design ofdielectric rod radiators. The narrow dimensions can be tapered asdesired to conform to the shape of an airfoil; however, this dimensionis shown as uniform in Fig. 1.

Due to the presence of the central web 9 of the H--shaped structure I ladjacent to radiators H! and [2, the radiation pattern of eitherradiator when it is energized is deflected in such a way that thedirection of maximum intensity in the electric plane is displaced awayfrom the longitudinal axis of the radiators and in a direction away fromthe opposite radiator.

Alternate excitation of radiators ill and I2 by means of a suitableswitching arrangement (not shown) provides a lobe-switching antennawhich can be used to secure accurate angular data or other informationreadily apparent to one skilled in the art. Prior art has establishedthe speci fications for suitable radiation pattern beam Widths and beamdeflections for such applications. Particularly satisfactory results aresecured when the radiation pattern beam widths, measured between thosedirections at which the intensity of radiated energy is one-half thepear; intensity, are 25 degrees and the deflection of the peak intensity01f the axis of the radiators in one plane is 9 degrees.

Fig. 2 shows a desirable means for providing excitation for the abovedescribed antenna, par

ticularly for those installations in which the physical restrictionsrequire the entrance of the coaxial transmission lines at the end or"the antenna rather than the top and bottom.

Dielectric rod radiators iii and i2 are disposed within the openchannels of an H-shaped structure comprising side pieces I and 8 and acentral web 9. A rectangular metal box 53 is provided, as before, toenclose the excitation means.

The inner conductor 2'. or" a coaxial transmission line it extendswithin box :3 a predetermined distance, being positioned centrally andparallel to the longitudinal axis or" radiator it. A metallic excitingprobe 22 is disposed perpendicularly to conductor 2!, substantiallyparallel to the narrow sides of radiator ill and at a predetermineddistance from the enclosed side of box is opposite the open side. Theopen end of probe 22 need not make electrical contact with the innerwall of box it, although satisfactory operation will be secured ifelectrical contact is made. Inner conductor 2! is extended apredetermined distance into rod radiator Iii beyond the junction withproble 22 to provide an impedance matching stub.

The vector direction of the electric component of the electromagneticfield excited within box l3 and radiator ill, when a source ofelectromagnetic energy (not shown) is connected to and energizes coaxialline 2%, is parallel to the narrow side walls or" radiator iii. Asimilar excitation assembly is provided, as shown in Fig. 2 below theabove described assembly, for the purpose of providing excitation forradiator it.

Since certain changes may be made in the above described apparatus, anddifierent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A lobe-switching antenna comprising, first and second dielectric rodradiators, a metallic structure having an H-shaped cross section formedby a central web and integral supporting side pieces, said radiatorshaving rectangular cross sections and being disposed within the openchannels of said H-shaped metallic structure, said radiators and saidmetallic structure being tapered together longitudinally, a rectangularmetal box having an open side, said central web and said first andsecond radiators extending within said box through said open side, andmeans for exciting within said box and separately within said first andsecond radiators electromagnetic fields, the vector direction of theelectric component of said electromagnetic fields being perpendicular tosaid central reflecting web.

2. Apparatus as in claim 1 in whic said exciting means comprises, firstand second coaxial transmission lines, said coaxial lines being fastonedto opposite sides of said box, the inner condoctor of said first coaxialline extending a predetermined distance through an opening in said boxand through one wide wall of said first radiator forming a firstexciting probe, the inner conductor of said second coaxial lineextending a predetermined distance through another opening in said boxand through one wide wall of said second radiator forming a secondexciting probe, said first and second exciting probes being positionedmidway between the narrow side walls of said radiators and at apredetermined distance from the enclosed side of said box opposite saidopen side.

3. Apparatus as in claim 1 in which said exciting means comprises, firstand second coaxial transmission lines, said coaxial lines being fastenedto the enclosed side of said box opposite said open side, the innerconductor of said first coaxial line extending through a first openingin said enclosed side and extending centrally within said first radiatorparallel to the longitudinal axis thereof, a first exciting probe ofpredetermined length fastened perpendicularly to said inner conductor ofsaid first coaxial line and parallel to the narrow walls of said firstradiator, said inner conductor extending a predetermined distance withinsaid first radiator beyond the junction with said first exciting probeto form a first impedance matching stub, the inner conductor of saidsecond coaxial line extending through a second opening in said enclosedside and extending centrally within said second radiator parallel to thelon itudinal axis thereof, and a second exciting probe of predeterminedlength fastened perpendicularly to said conductor of said second coaxialline and parallel to the narrow walls of said second radiator, said lastmentioned inner conductor extending a predetermined distance within saidsecond radiator beyond the junction with said second exciting probe toform a second impedance matching stub, said first and second excitingprobes being positioned a predetermined distance from said enclosedside.

4. A lobe-switching antenna comprising, in combination, a conductivereflecting member, first and second dielectric radiators disposed on andin lateral contact with the opposite sides of said member, and meansassociated with said radiators for separately exciting electromagneticfields within said first and said second radiators.

5. A lobe-switching antenna comprising, a metallic structure of H-shapedcross-section, first and second rectangular dielectric rod radiatorsdisposed within the open channels of said H- shaped structure, anadapting member enclosing one end of said metallic structure and saidradiators, and separate exciting means connected to each of saidradiators through said adapting member.

6. A lobe-switching antenna comprising, a conductive central member, aplurality of dielectric radiators arrayed about said central member andin lateral contact therewith, and means associated with said radiatorsfor separately energizing said radiators.

'7. A lobe-switching antenna comprising, a tapered metallic structure ofH-shaped cross section, first and second tapered dielectric radiators ofrectangular cross section disposed in and conforming to the channels ofsaid Hmhaped metallic structure, and means associated with saidradiators for separately energizing said radiators.

S. A lobe-switching antenna comprising, a tapered metallic structure ofH -shaped cross section, first and second tapered dielectri radiators ofrectangular cross section disposed in and conforming to the channels ofsaid l-l-shaped metallic structure, an adapting member of rectangularcross section enclosing the large end of said tapered dielectricradiators, a portion of said central member being arranged to dividesaid adapting member into separate compartments, one of saidcompartments communicating with each of said dielectric radiators, and aprobe extending 5 into each of said compartments for separatelyenergizing said radiators.

9. A lobe-switching antenna comprising, a conductive reflecting member,first and second dielectric radiators substantially coextensive withsaid member and disposed on opposite sides of said member, and meansassociated with said radiators for separately exciting said radiators.

10. A lobe-switching antenna comprising, a

metallic member of H-shaped cross-section, and 10 individual dielectricmeans disposed within the open channels of said metallic member andconstituting independent Wave energy radiators.

11. Apparatus as in claim 10 wherein the dielectric means have arectangular cross-section. 15

12. A lobe-switching antenna comprising, a metallic member of H-shapedcross-section, and separate dielectric radiators disposed within theopen channels of said metallic members.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,129,711 Southworth Sept. 13, 1938 2,216,708 Kolster Oct. 1,1940 2,337,324 Granqvist Dec. 21, 1943 2,425,336 Mueller Aug. 12, 19472,460,401 Southworth Feb. 1, 1949 2,473,446 Riblet June 14, 1949

